Dark matter accounts for the motion of groups of galaxies called clusters, which is not easily explained by visible matter alone.

Although its composition is not known, astronomers estimate that dark matter makes up approximately 23% of the universe.

Dark energy, which accounts for almost three quarters of the universe's mass, is a force that works against gravity and helps explain why the expansion of the universe is accelerating.

The existence of dark energy and dark matter has been confirmed by numerous astronomical observations. But, despite much conjecture, the link between the two is unknown.

Decaying away

Abdalla and colleagues from Brazil and China believe they have found a connection between the two - dark energy is decaying into dark matter.

To reach this conclusion, the researchers calculated the mass of 33 galaxy clusters, studying x-rays, optical light and gravitational lensing effects. They then used these mass estimates in a standard mathematical model of galaxy clusters.

The models were ran assuming no link between dark energy and dark matter, and were then repeated using the assumption that dark energy decays into dark matter.

Their results showed that when dark energy and dark matter were linked, the model more closely predicts the clusters' behaviour.

The researchers say more galaxy clusters need to be measured and tested to confirm their result.

"If a significant indication of such coupling [between dark matter and dark energy] is still found, this would open a tantalising new window on the nature of the dark sector," the researchers write.

Australian astrophysicist Associate Professor Scott Croom of the University of Sydney says the research is a "nice way to get a different angle on the question of dark matter".

But Croom questions whether astronomers could ever get measurements of the mass of clusters accurate enough to confirm the link.

"It's hard to put your finger on what exactly [the result] means, because we're still groping around in the dark in terms of trying to understand [dark matter and dark energy]," he says.